Electrical stethoscope



June 2, 1925. 1,540,585

R. B. ABBOTT ELECTRICAL STETHOSCOPE Filed Oct- 27. 1922 A TTORNEYSPatented Jane 2, 1925.

UNITED STATES RAYMOND BARRINGTON ABBOTT, F WEST LAFAYETTE, INDIANA.

ELECTRICAL STETHOSGOPE.

Application filed October 27, 1922. Serial No. 597,497.

To all whom it may concern:

Be it known that I, RAYMOND B. Annor'r, a citizen of the United States,and a resident of West Lafayette, in the county of Tippe-' canoe andState of Indiana, have invented a new and Improved ElectricalStethoscope, of which the following is a full, clear, and exactdescription.

This invention relates to electrical stethoscopes. I In contemplatingthe invention, consideration must be given to the fact that in using aninstrument of this sort the beats which are generally measured arethoseof very low frequency, and it must necessarily be understood thatthe ordinary electrical de vice for transmitting sound, such as atelephone transmitter, is not especially adaptable to use as astethoscope because the diaphragm of such transmitter is tuned tofrequencies far different than those which are measured when using anordinary stethoscope. If, therefore, an electrical sound transmitterdevice, such as an ordinary telephone transmitter, particularly anespecially sensitive one, is properly treated it can be made to respondto vibrations or variations in sound produced within a narrow limit offrequency ranges; therefore, it can be and has been tried, in accordancewith my invention, to make it respond only to those vibrations which arewithin the range of those corresponding to the frequency of vibrationsof the heart action in the human body. If the transmitter can be tunedto this type of frequency, then it is true that other sounds occurringin the immediate vicinity of the instrument are not received clearly ifat all.

To this end, therefore, my invention has for an object the provision ofa telephone transmitter with the vibrating parts so arranged andconstructed as to be responsive with a high degree of sensitiveness tolow frequency vibrations, such as those produced by the heart beat, andto be practically nonresponsive to any other frequencies of beats.

Another object is to provide an electrical sound-receiving device, suchas a telephone transmitter, modified by the application thereto of myinventive idea, the application of which to the transmitter, however,does not involve any such change in the transmitter as will require itsbeing rebuilt or redesigned. In other words, my inventive idea can bereadily applied to any ordinary telephone transmitter of a degree ofsensitiveness suitable for the requirements of the work.

The invention is illustrated in the draw- 1ngs, of which- Figure 1 is asection taken through the transmitter.

Figure 2 is a section taken on the line 2-2 of Figure 1.

The form of the invention shown in the drawing is a preferred form,although it is understood that modifications in the construction andarrangement of the parts and in the character of the materials usedmaybe adopted without departing from the spirit of the invention.

'As illustrated in the drawings, the preferred form of the inventionincludes a cupshaped metallic casing 1 having a central aperture 2 intowhich the usual mouthpiece 3. preferably of hard rubber, is screwed.This mouthpiece, in the operation of the device in accordance with myinvention, is provided with a plain thin diaphragm 4, preferably of somematerial such as hard rubber or celluloid. Thisdiaphragm may be fastenedto the end of the mouthpiece by any suitable means, such as adhesive.The metallic casing 1 has a back plate 5 screwed thereto. This backplate provides a support for a plurality of stub shafts such as 6 and 7supporting resistance cells 8, preferably containing material such as 9,which may be and generally is loose in granular carbons. These cellswith the contained carbon are similar to the ordinary telephonetransmitter buttons The resistance to the flow of current through thecarbon is varied as the pressure upon the carbon granules is varied. Theends of the cells 8 are connected to a diaphragm 10, preferably made ofthin metal, brass or aluminum. This diaphragm is held in the metal case1 by means of felt washers 10 disposed on either side and held in placeby a metal ring 10*. This ring and these washers are held in the casingby being disposed between its front wall and the back plate 5. Thecenter of the back plate 5 is apertured to receive a hard rubber screwlug 11 to which a connection 12. is made by wire 13 to the diaphragm 10.and then back through the buttons or cells 8 to the back plate 5, to awire 14, which may be connected to a suitable devicesuch as a battery 15in circuit with which is a primary 16 of a transformer, the secondary 17of which is connected by wires 18 and 19 to any suitable electricaldevice 20, which may be a receiver or an amplifier. The battery 15 isconnected by a wire 21 to a pin 22 extendin through the screw plug 11.The back of the metallic casingl is covered and the parts exposedthereon are enclosed by a thin metal shell 23 fastened to the casing byany suitable means, such as aset screw 24.

In order to provide that the diaphragm 10 shall vibrate only to thosevfrequencies which lie within a narrow and desired range, I pass a pin 25through the central portion of the diaphragm 10 and on this pm I dlsposea plurality of washers 26, preferably of lead, so as to weight or'loadthe diaphragm 10. This loading of the diaphragm will slow down thesensitiveness of the diaphragm to other vibrations than those of lowfrequency.

It will thus be seen that in the transmitting device above describedthere is an air chamber to the left of the diaphragm 10 containing thecarbon buttons and a dead air chamber to the right of the diaphragm 10and between it and the diaphragm 4 into which the load elements, such asthe pin 25 and the washers 26, extend. The pin or bolt is preferablyformed of brass. As the thin diaphragm a is placed against the organism,the movement or vibration of which is to be measured, the air within thechamber contained between this diaphragm and the diaphragm 10 will bemoved by the movement of the diaphragm 4 and cause a movement of thediaphragm 10 which is regulated or limited by the depression of theweight in the form of the plurality of washers on this diaphragm.Therefore, the loaded diaphragm will respond to the particularvibrations to which it is sensitive and will so affect the carbon cellsor buttons as to cause a variation of current in the circuit which maybe received or amplified as desired.

What I claim is 1. In an electrical stethoscopic device, means forproviding a dead air chamber, a thin diaphragm forming one end wall ofthe dead air chamber said diaphragm being mounted for free vibratorymotion and adapted to freely transmit vibrations to the dead airchamber, a weighted diaphragm forming the other end wall of the chamber,and means whereby vibrations of the last named diaphragm may beconverted into electrical signal currents.

2. An electrical stethoscopic device which includes a sound chamber, athin diaphragm across one end of said chamber, a metallic diaphragmdisposed across the other end of said chamber, rod extending throughsaid diaphragm into said chamber, and a plurality of weights disposed onsaid bar to vary the sensitiveness of the diaphragm to vibrationsproduced in the chamber by the vibrations of the first mentioneddiaphragm when placed against a vibrating organism.

RAYMOND BARRINGTON ABBOTT.

